This invention relates generally to lighting fixtures for theater, architectural and television lighting applications and, more particularly, to light source assemblies, or light engines, incorporating light-emitting diodes (“LEDs”) that are configured as retrofit assemblies for attachment to lighting fixtures previously incorporating incandescent lamps.
Theater, architectural and television lighting fixtures for projecting high-intensity beams of light traditionally have included an incandescent lamp mounted by a burner assembly to a concave reflector, with the lamp's filament(s) located at or near a focal point (or region) of the reflector. A lens assembly is located forward of the lamp and reflector. In use, light emitted by the lamp is reflected in a forward direction by the concave reflector, and the lens assembly in turn projects the reflected light forward along the fixture's longitudinal axis. One type of these fixtures includes a concave reflector having a generally ellipsoidal shape, and the lamp filament(s) is/are located at or near the reflector's near focal region. A gate is located at or near the reflector's second focal region, and the lens assembly images the light passing through the gate at a distant location, e.g., a theater stage. Another type of these fixtures includes a concave reflector having a generally parabolic shape, and the lamp filament(s) is/are located at or near the reflector's single focal region. In this case, the lens assembly simply projects the reflected light in a forward direction, to bathe, or “wash,” the distant location.
Lighting fixtures of this type have enjoyed widespread use in the theater, architectural and television lighting fields. Hundreds of thousands of such fixtures are sold every year. However, because of recent advances in the development of high-intensity light-emitting diodes (“LEDs”), the incorporation of incandescent lamps in such fixtures is in some cases now considered unduly wasteful of energy. In addition, such incandescent fixtures generally require frequent servicing due to the relatively short lifetime of incandescent lamps. Efforts, therefore, have been made to retrofit such lighting fixtures by substituting LED arrays for their incandescent lamps.
One effort to configure an LED lighting fixture that utilizes components of prior incandescent lamp lighting fixtures is described in U.S. Patent Application Publication No. 2012/0140463, filed in the name of David Kinzer et al. The disclosed fixture includes a planar array of LEDs mounted at the rear end of an elongated mixing tube assembly, which in turn is mounted to a conventional gate and lens assembly. The mixing tube assembly includes a reflective inner surface having a converging section and diverging section, which function to homogenize the light emitted by the planar LED array. In use, light from the LED array is directed through the mixing tube assembly for mixing, and from there through the gate and lens assembly for projection toward a distant location.
Kinzer's lighting fixture is effective in projecting a high-intensity beam of light using less electrical power than prior incandescent lamp lighting fixtures (30 versus 20 lumens per watt, field efficacy). However, when its design is used as a retrofit of prior incandescent lamp lighting fixtures, it is considered to include an excessive amount of replacement structure and to utilize an unduly small proportion of the prior fixtures, i.e., only the gate and lens assemblies of such prior fixtures. As a retrofit, this design is not considered to be particularly cost-effective and it cannot be easily installed with the fixture in situ. The Kinzer fixture also has poor soft focus characteristics because it images the LED array in the far field.
It should, therefore, be appreciated that there remains a need for a more cost-effective way to retrofit prior incandescent lamp lighting fixtures for use with LED light sources. In particular, there is a need for an LED light source assembly that can be combined with a greater proportion of such prior incandescent lamp lighting fixtures. The present invention fulfills this need and provides further related advantages.